Mexico City’s rainy torment

They’re calling for rain today, but that’s no surprise. Predicting rain on a summer day in Mexico City is like forecasting death in an old-folks home. It’s bound to happen.

From springtime to autumn, it rains a lot here. Let me be clear: a lot.

The Mexico City government issues the same monotonous forecast each day: 80% or higher chance of rain. The only suspense is whether it will come with lightning or hail.

It’s the same almost every afternoon — you could set a clock, if the power hasn’t been knocked out. People schedule outdoor parties early, knowing that by late afternoon, the storm clouds will prevail. During the sodden last week, the rains haven’t even waited past noon.

Look up most days, and the sky’s an inscrutable jumble: cottony clouds bump up against slate-gray masses, while ominous black streaks make threats in one direction and portholes of blue sky make promises in another.

Apres that, the deluge. The rains arrive aboard lashing winds that topple trees or hunker lazily in place for hours. The only sure thing is that the sunshine is done for the day.

True, the daily downpours do offer a cleansing sensation in a city coated in the grime of tens of thousands of pollution-belching buses and taxis. When it rains, the sidewalks — scrubbed each morning in well-to-do neighborhoods by maids with brooms and buckets of soapy water — are rinsed of the leaves and dog poop that invariably build up in the few hours between the work of the maids and the work of Mother Nature.

Mostly, though, the rainy season in Mexico City can feel like living under a grinding, water-logged siege. Mexico City was a lake long ago, and each time there’s a gusher, it flirts with its former identity.

Newspapers tally the overnight ponds and fallen trees, and inevitably report on whatever caos vial, or road chaos, was unleashed by the latest storm (as if the usual state of Mexico City’s streets were something other than a gigantic, honking mess).

Even modest storms knock out electricity in apartment buildings, or entire blocks, for hours at a time. The canny makers of a voltage-regulation device are airing a special, rainy-season commercial reminding shoppers how unreliable their power supply can be.

Vacant taxis, which most days careen about in endless supply, are as scarce as if they’d been beamed to some planet blessed with nice weather that lasts.

How fitting that the Spanish word for storm is tormenta.

From June through October, Mexico City gets the lion’s share of its annual rainfall — 34 inches, or 14% more than famously soggy London.

The Mexican capital is perched at 7,500 feet, a cool-weather zone where warm, moist air masses from southern and coastal areas often come together, ardently it seems.

Throw in the odd low-pressure system, the side effects of a distant hurricane, and you’ve got a season of wet feet.

A heavy storm can spell disaster. Hundreds of homes were swamped by raw sewage last year after rains overwhelmed a drainage canal in eastern Mexico City. It’s best not to be caught without your waders.

But you can go too far in expecting the worst, as Mayor Marcelo Ebrard discovered last week when he went public with an unusually stark warning that the city was about to be pounded by days of severe rain.

Ebrard, who wants to run for president in 2012, mobilized rescue workers and warned residents to stay inside for the next three days.

Then it hit: drizzle. OK, drizzle with periods of moderate rain, but nothing approaching the biblical. Residents rolled their eyes, and radio pundits mocked Ebrard as an attention-seeking Chicken Little.

Undaunted, Mexico City officials issued a new severe-weather alert two days later. It poured for hours. Buckets. In summer, predict bad rains here all you want. Sooner or later, you’re sure to be right.

ken.ellingwood@latimes.com